Meta-Optics-Based Systems and Methods for Ocular Applications

ABSTRACT

Meta-lens based ocular imaging, near-eye display, and eye-tracking systems are described. The systems can include a single focusing optic and an integrated circuit that provides illumination light and includes an imaging array. The focusing optic includes meta-atoms formed on a substrate. The systems may have no moving parts and achieve imaging or image-projection fields-of-view approaching or exceeding 180 degrees. Because of their low part count, the systems can be robust and have a very small form factor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims a priority benefit, under 35 U.S.C. § 119(e), ofU.S. Application No. 63/003,782, filed on Apr. 1, 2020 titled, “FlatOptics-Based Systems and Methods for Ocular applications, which isincorporated herein by reference in its entirety.

GOVERNMENT SUPPORT

This invention was made with Government support under Grant No.HR0011-1-72-0029 awarded by the Defense Advanced Research ProjectsAgency (DARPA). The Government has certain rights in the invention.

BACKGROUND

Wide-angle optical imaging and projection systems are desirable forhigh-performance, wide field-of-view (FOV) imaging and projectionapplications. One of the earliest examples of a wide-angle opticalsystem is the panoramic camera invented by Thomas Sutton in 1858. Thispanoramic camera included a single water-filled spherical lens thatproduced an image on a curved glass plate covered with reactiveemulsion. Due to difficulties in fabrication and handling of curvedplates, this approach was soon abandoned. Panoramic photography thenevolved using planar detector planes while relying on compound lensassemblies, commonly known as fisheye lenses, to reduce opticalaberrations at large viewing angles. Such a multi-lens architecture,however, increases the size, weight, assembly complexity, and cost ofoptical systems.

Fundus cameras have been widely used in retinal photography for thediagnosis and monitoring of retinal diseases. These cameras are used toimage a large interior region of the eye and therefore benefit from wideFOV optics. For example, a fundus camera desirably should be capable ofimaging a large region of the retina, sclera, or other tissues insidethe eye. Imaging large regions in a single photo can require FOVsapproaching 180 degrees.

Most conventional approaches to ocular imaging, like panoramic cameras,use complex lens systems to obtain wide FOVs. Fundus cameras are usuallydesigned to illuminate and image the retina simultaneously using sharedoptical paths. Such optical systems are complicated and typicallyinclude a series of objective and condensing optical elements, beamsplitters, mirrors, shadowing masks, diffusers, polarizers, lightsources and photodetectors. State-of-the-art fundus cameras can begenerally categorized into three groups: table-top fundus cameras,miniaturized handheld ophthalmic cameras, and smart-phone-basedophthalmic cameras. Challenges associated with these existingtechnologies involve limited FOV, complicated illumination/imagingco-design, and poor signal-to-noise ratio. For example, cameras in eachof the three groups have stacked or compound lenses and combineillumination and imaging optical paths. To date, high-quality, wide FOVretinal imaging is only offered by table-top fundus cameras built fromcomplex and bulky optical systems. These cameras are large and expensiveand must be operated at high-end and expensive clinical settings.

SUMMARY

Compact, wide field-of-view ocular imaging systems are described thatare based on meta-lenses. The meta-lens can be a single flat-opticimaging element that can capture images over a FOV approaching 180degrees or larger and focus the images onto an essentially flat or acurved focal plane. An ocular imaging system using a meta-lens may alsouse the pupil of the eye as an aperture stop for the imaging system toobtain high-resolution images. Such ocular imagers may be no thickerthan 20 mm and have an input located a distance between 1 mm and 100 mmfrom an eye to obtain wide FOV, high-quality images of interior regionsof the eye. In some cases, they can also be configured to be positionedin direct contact to the eye, or in contact via an intermediate layer,such as a contact lens or an immersion fluid layer positioned betweenthe imager and the eye.

Such imaging systems can also be operated in reverse as a near-eyedisplay systems. Instead of receiving images onto a detector array atthe system's focal plane, the imaging systems can project wide-fieldimages from the focal plane onto the retina or nearby screen for userviewing (e.g., for augmented reality (AR) or virtual reality (VR)).Variations of the near-eye display systems may also be used foreye-tracking applications. Because the imaging and near-eye displaysystems can have only a single focusing optic and no moving parts, theimagers and display systems can be compact, robust, and light-weight foreasier deployment and use than conventional systems. The meta-lens basedsystems may have unprecedented size, weight, power and cost (SWaP-C)advantages compared to traditional bulk optical systems.

Some implementations relate to ocular imaging systems that comprise asubstrate having a first surface with a meta-lens formed thereon. Themeta-lens comprises an imaging zone having a first plurality ofmeta-atoms, wherein the meta-lens is to be positioned within 40 mm orwithin 100 mm of an eye's pupil to image an interior portion of the eye.The ocular imaging system may further include a light source toilluminate an interior of the eye and an array of photodetectors locatedat a focal surface of the meta-lens to detect an image of the interiorportion of the eye that is formed by the imaging zone.

Some implementations relate to methods of operating an ocular imagingsystem. Such methods may comprise acts of: directing light from a lightsource toward an eye; collimating, focusing, or patterning the lightwith an illumination zone of a meta-lens, the illumination zonecomprising a first plurality of meta-atoms formed on a substrate;focusing light reflected from the eye with an imaging zone of themeta-lens, the imaging zone comprising a second plurality of meta-atomsformed on the substrate; and detecting the focused light with an arrayof photodetectors.

Some implementations relate to near-eye display systems that comprise asubstrate having a first surface with a meta-lens formed thereon. Themeta-lens comprises a plurality of meta-atoms, wherein the meta-lens isto be positioned within 40 mm or within 100 mm of an eye's pupil. Suchnear-eye display systems may further include a micro-emitter array ormicro-display located within 10 mm of the substrate to form an imagethat is projected by the meta-lens directly onto the retina of the eye,wherein the image covers a field-of-view between 70 degrees and 200degrees as measured around the interior of the eye.

Some implementations relate to eye-tracking systems that comprise anemitter to produce illumination light and a first meta-lens that iswithin 10 mm of the emitter and within 40 mm or within 100 mm of an eye.The first meta-lens may include a first plurality of meta-atoms formedon a surface of a first substrate and arranged to project a pattern ofthe illumination light onto the eye. The eye-tracking systems mayfurther include a second meta-lens located within 40 mm or within 100 mmof the eye's pupil. The second meta-lens may include a second pluralityof meta-atoms arranged to image a region of the eye illuminated by thepattern and an imager having a plurality of photodetectors to record animage of the region of the eye.

All combinations of the foregoing concepts and additional conceptsdiscussed in greater detail below (provided such concepts are notmutually inconsistent) are part of the inventive subject matterdisclosed herein. In particular, all combinations of claimed subjectmatter appearing at the end of this disclosure are part of the inventivesubject matter disclosed herein. The terminology used herein that alsomay appear in any disclosure incorporated by reference should beaccorded a meaning most consistent with the particular conceptsdisclosed herein.

BRIEF DESCRIPTIONS OF THE DRAWINGS

The skilled artisan will understand that the drawings primarily are forillustrative purposes and are not intended to limit the scope of theinventive subject matter described herein. The drawings are notnecessarily to scale; in some instances, various aspects of theinventive subject matter disclosed herein may be shown exaggerated orenlarged in the drawings to facilitate an understanding of differentfeatures. In the drawings, like reference characters generally refer tolike features (e.g., functionally and/or structurally similar elements).

FIG. 1 depicts an elevation view of a wide field-of-view (WFOV)meta-lens.

FIG. 2A shows a perspective view of a cylindrical pillar meta-atom for aWFOV meta-lens.

FIG. 2B plots transmittance and phase of cylindrical pillar meta-atomsfor a WFOV meta-lens that are designed for an operating wavelength of940 nm.

FIG. 2C plots phase of cylindrical pillar meta-atoms for a WFOVmeta-lens that are designed for an operating wavelength of 680 nm.

FIG. 3 is a scanning electron micrograph showing meta-atoms included ina portion of a meta-lens.

FIG. 4 depicts an example of an ocular imaging system that uses acompact meta-lens.

FIG. 5A depicts an example of a meta-lens for an ocular imaging system.

FIG. 5B depicts another example of a meta-lens for an ocular imagingsystem.

FIG. 5C depicts another example of a meta-lens for an ocular imagingsystem.

FIG. 6 depicts another example of an ocular imaging or near-eye displaysystem that uses a compact meta-lens and a relay optic.

FIG. 7 depicts an example of a near-eye display system that uses acompact meta-lens.

FIG. 8A depicts an example of an eye-tracking system that uses compactmeta-lenses.

FIG. 8B depicts another example of an eye-tracking system that usescompact meta-lenses.

FIG. 8C depicts another example of an eye-tracking system that usescompact meta-lenses.

FIG. 9 illustrates acts that may be included in a method of operating anocular imaging system.

DETAILED DESCRIPTION

Meta-lenses are compact optical elements that have microfabricatedstructures (called meta-atoms) formed on a transparent substrate. Themeta-atoms are designed and located on the substrate to give themeta-lens its desired optical characteristics, which can be tailored fora particular application by an optical engineer. Because of their smallsize, lack of moving parts, robustness, and flexibly tailored opticalcharacteristics, meta-lenses can be useful for various applications suchas, but not limited to, augmented reality (AR), virtual reality (VR),heads-up display, near-eye display, three-dimensional (3D) sensing,holography, LIDAR, and Fourier transform optics. An optical system basedon a meta-lens can have significant size, weight, performance, and cost(SWaP-C) advantages over a system made of traditional opticalcomponents. A meta-lens that is tailored for wide FOV imaging can beuseful for ocular imaging and near-eye display, as described furtherbelow.

FIG. 1 depicts an example of a meta-lens 100, which is monolithicallyintegrated on a flat transparent substrate 110. The meta-lens includesan aperture stop 130 on a first surface 112 and a meta-surface 120comprising meta-atoms formed on a second surface 114 of the substrate110. For the illustrated example, the meta-atoms of the meta-surface 120are arranged to focus collimated light received over a wide FOV onto aplanar focal plane 150, as depicted in the drawing. An integratedcircuit 180 (e.g., detector array, emitter array, and/or micro-display)can be placed at the focal plane 150 for image acquisition or imageprojection. Such a meta-lens can be used for wide-angle ocular imaging,near-eye display, and eye-tracking systems. Wide-angle ocular imaging,in particular, is desirable since it can address a wide range ofdiseases such as diabetic retinopathy, retinal vein occlusions,retinopathy of prematurity, retinal detachment, choroidal masses,uveitis, retinal vasculitis, etc.

The substrate 110 may be made of any suitable material that transmitslight at the meta-lens's operating wavelength. The substrate 110 may berigid, flexible, or stretchable and can be flat/planar on both sides, asshown in FIG. 1. In some cases, one or both surfaces of the substratemay be curved (e.g., concave or convex). For example, the substrate 110may have a spherical, cylindrical, or free-form lens shape. In somecases, the substrate 110 may be warped, curved, or bent, depending onthe application. Suitable substrate materials include but are notlimited to calcium fluoride, halide crystals, sapphire, and other oxidecrystals, quartz, silica, fused silica, chalcogenide crystals, glass(e.g., oxide, chalcogenide, as well as other types of glass), opticalpolymers, or semiconductor materials. The substrate material can betransparent and exhibit low loss (e.g., less than 10%) at the operatingwavelength of the meta-lens. The substrate 110 has a refractive index ofn_(sub) and a thickness of t_(sub). Light beams entering the inputaperture 132, which has a diameter of D_(in), at different incidenceangles θ_(in) are refracted to the backside meta-surface 120, which hasa total diameter of D_(meta). The light beams are then focused by themeta-surface's meta-atoms onto the planar focal plane 150.

The aperture stop 130 can be formed as a layer 134 of opaque material(e.g., absorptive or reflective metal or semiconductor material) on thefirst surface 112 of the substrate 110. In one example, the aperture 132can be circular with a diameter given by:

$\begin{matrix}{D_{in} = {D_{meta} - {2t_{sub}\mspace{14mu}{\tan\lbrack {\sin^{- 1}( {1/n_{sub}} )} \rbrack}}}} & (1)\end{matrix}$

This diameter can range from microns to millimeters, with a numericalaperture (NA) that ranges from 0 to 1. The numerical aperture can behigher (e.g., 1.5) if the meta-lens is immersed in oil or otherhigh-index material.

The aperture 132 can be square, elliptical, hexagonal, rectangular, orany other suitable shape in other implementations. Alternatively, theaperture can include one or more sub-apertures, sub-regions, patches, orarrays configured to modulate or encode the input light in one or moreof spectrum, phase, amplitude, polarization, etc. For example, at leasta portion of the aperture 132 may be patterned with meta-atoms thatfilter light passing through the aperture 132. If desired, the edge ofthe aperture stop 130 can be apodized, e.g., with a Gaussian orsuper-Gaussian apodization, to reduce deleterious edge effects thatmight arise from an abrupt edge of the aperture.

In some ocular imaging implementations, the aperture stop 130 andaperture 132 may not be included on the substrate 110. Instead, thepupil of a subject's eye or an aperture positioned near the eye (e.g.,an artificial aperture on a contact lens) may be used as the aperturestop for an ocular imaging or near-eye projection optical system. Insuch cases, the meta-lens 100 may be specified for use in closeproximity to the eye (e.g., within 100 mm, within 40 mm, within 20 mm,within 10 mm, or within 5 mm from a surface of the eye). The specifieddistance may be between a designated location on the meta-lens (e.g.,its rear meta-surface 120) or a location on the assembly in which it ismounted (e.g., a mark on the assembly) and a designated feature of theeye (e.g., cornea, exterior surface, or pupil). In some cases, theworking distance of a meta-lens may be between 4 mm and 11 mm tomaintain a FOV greater than 60 degrees.

In some implementations, the ocular imaging system may includerange-finding apparatus to aid a user in positioning the meta-lens 100 acorrect distance from the eye. For example, the integrated circuit 180may include one or more laser diodes and the meta-lens include anillumination zone described further below that projects a pattern ontothe eye, which can be imaged back on the focal plane 150 and integratedcircuit 180 by the meta-lens. The image of the pattern can be processedto determine a distance between the meta-surface 120 and pupil, forexample.

The meta-surface 120 includes a plurality of meta-atoms (sometimesreferred to as Huygens meta-atoms, nano-antennae, or nano-structures)that modify the amplitude, phase, and/or polarization of incoming wavefronts. These meta-atoms can have sub-wavelength feature sizes (invertical and/or transverse dimensions), wherein the reference wavelengthis the designed operating wavelength for the meta-lens. The meta-atomsmay be 0.01 wavelength to 100 wavelengths thick. There can be one ormore types of meta-atoms formed on the substrate's meta-surface 120. Forexample, the meta-atoms may have one or more of the following shapes:square, rectangular, bar, beam, cylindrical or elliptical (pillars ordiscs), rings, crosses (+), X-shaped (x), V-shaped, H-shaped, L-shaped,or freeform shapes. The shapes are not so limited, and other shapes maybe used.

The types of meta-atoms may be categorized into three groups: resonatingstructures, vertical waveguiding structures, and geometric phase-basedstructures. There may be more than one size and shape of meta-atoms ineach of these three groups. In some cases, a same meta-atom shape may beused in two or more of the groups. The resonating structures includeHuygens meta-atoms and may have one or more dimensions that is anintegral number of half-wavelengths of the designed operatingwavelength, divided by the refractive index of the material from whichthe meta-atom is made. Accordingly, the operating wave may resonate inthese structures. The vertical waveguiding structures may form avertical waveguide for the operating wavelength. The phase-basedstructures may be designed to impart a desired phase shift to TE and/orTM waves passing through each unit cell containing a meta-atom orpassing through a portion of the meta-surface 120 containing adjacentidentical unit cells. A meta-surface may be formed using one type ofmeta-atom or a combination of two or three types of meta-atoms.

The meta-atoms can be arrayed on a lattice with a pitch that is lessthan or equal to the operating wavelength of the meta-lens 100. Thelattice can have any suitable structure (e.g., square, rectangular, orhexagonal). The lattice can be periodic, semi-periodic, aperiodic, orrandomly spaced for example, with lattice spacing defined by acenter-to-center distance between adjacent meta-atoms. The meta-atoms'shapes, sizes, and layout can be selected so that the meta-surface'sspectral response does not change with angle of incidence. Themeta-atoms can be shaped and located to provide a desired phase profileover the entire meta-surface 120. In some cases, the first surface 112may additionally have meta-atoms patterned thereon to further controloptical characteristics of the meta-lens 100. Further details ofmeta-lens design, fabrication, and operation can be found in U.S. patentapplication Ser. No. 16/894,945 titled “Ultra-Wide Field-of-View FlatOptics,” filed Jun. 8, 2020, which application is incorporated herein byreference in its entirety.

FIG. 2A shows a perspective view of a cylindrical pillar meta-atom 210.Depending on its size and material used, a cylindrical pillar meta-atommay be used as a resonating meta-atom, vertical waveguiding meta-atom,or geometric phase-based meta-atom. The meta-atom 210 has a height Hextending from the surface of the substrate 110 and a diameter D. Forthe illustrated example and graphs of FIG. 2B and FIG. 2C, the meta-atom210 is formed from amorphous silicon and the substrate 110 is formedfrom sapphire. The meta-atom 210 is located in a square-shaped unitcell, and there can be thousands to millions of such unit cellsdistributed side-by-side across the surface of the substrate 110 in asquare lattice. The diameters D and/or heights H of the meta-atoms 210can be varied among the unit cells across the surface to obtain thedesired spatial phase characteristics across the surface of thesubstrate 110.

As one example, a metal-lens for ocular imaging at an operatingwavelength of 680 nm may have a meta-surface 120 with cylindrical pillarmeta-atoms 210 of eight different diameters that are distributed acrossthe meta-surface 120. The heights H of the meta-atoms may be the same(e.g., 800 nm). The unit cell may be square and measure 320 nm on eachside. The eight diameters of the meta-atoms 210 are listed in Table 1.

TABLE 1 Diameters of example cylindrical pillar meta-atoms for ameta-lens. Meta-atom number 1 2 3 4 5 6 7 8 D(nm) 90 100 112 120 150 156166 185

FIG. 2B plots phase characteristics of unit cells of a meta-surface 120having cylindrical pillar meta-atoms 210. The meta-atoms may havediameters as listed in Table 1. The eight meta-atoms with various phasedelays can cover a phase range of approximately 360 degrees with stepsof about 45 degrees.

FIG. 2C shows transmittance and phase characteristics for differentmeta-atoms that can be used for a longer-wavelength application. Thetransmittance and phase are plotted as a function of pillar diameter Dfor unit cells containing cylindrical pillar meta-atoms 210. The pillarsare formed from amorphous silicon and the substrate 110 is sapphire.These meta-atoms are designed for a meta-lens having an operatingwavelength of 940 nm. Eight pillar diameters ranging from about 130 nmto about 230 nm can provide various phase delays over a range of about360 degrees with steps of about 45 degrees and transmittance above 90%.

Materials other than silicon may be used for the meta-atoms. Forexample, various dielectric, semiconductor, or metal materials may beused for the meta-atoms that are amenable to micro-fabricationprocesses. Example semiconductor materials include, but are not limitedto, silicon-carbide, indium-phosphide, gallium-nitride,gallium-arsenide, etc. Other meta-atom materials include silicon nitride(SiN_(x)) and titanium dioxide (TiO₂). Lead telluride (PbTe) can be usedas a meta-atom material with a calcium fluoride (CaF₂) substrate formid-infrared wavelengths. The meta-atoms can also be directly etchedinto a substrate, e.g., a silicon substrate.

In some cases there may be no more than 10 different shapes ofmeta-atoms on a lens' meta-surface 120. However, fewer or more shapesmay be used for some implementations. In some cases, there may be atleast two different shapes of meta-atoms on a lens' meta-surface 120. Insome cases, there may be up to 100 or more different shapes ofmeta-atoms on a lens' meta-surface 120.

FIG. 3 depicts a portion of a meta-lens' meta-surface 120 designed for amid-IR imaging application. An array of meta-atoms 300 are patternedacross the surface 114 of the substrate. The meta-atoms includerectangular and H-shaped structures arranged on a square lattice(2.5-micron pitch). In some implementations, similar shapes and/or sizesof meta-atoms may be located within radial bands on the substrate. Forexample, there may be a plurality of cylindrical pillar meta-atomshaving a same diameter located within a radial band on a meta-surface.There may be a plurality of different radial bands containing differentshapes formed on the substrate. The different radial bands may extendacross portions of the meta-surface 150 to define desired phasecharacteristics of the meta-surface.

By spatially decoupling the meta-surface 120 and aperture stop 130, themeta-lens 100 can capture input beams at different angles of incidence(AOIs) on different yet continuous portions of the meta-surface 120.This can allow local tailoring of the lens' phase profiles, e.g., byoptimizing against a figure of merit that accounts for focusing qualityat multiple AOIs. The meta-surface phase profile can be designed so thatthe root-mean-square (RMS) wave front error from an ideal spherical wavefront over the input aperture is always smaller than 0.0745 wavelengths.With such low wavefront errors, the meta-lens 100 can have a Strehlratio of over 80% (and achieve near diffraction-limited performance)over a very wide field-of-view, which can be 120°, 130°, 140°, 150°,160°, 170°, 175°, 179°, or nearly 180° for a flat substrate 110. Formeta-lens with a curved, bent, or warped substrate, the field-of-viewcan be 180° or larger. Such large FOVs can be beneficial for ocularimagers and near-eye display systems.

Such meta-lenses can have meta-surfaces that correct one or morethird-order Seidel aberrations, including coma, astigmatism, and fieldcurvature. An example meta-lens 100 for an ocular imager or near-eyedisplay system can have an aperture 132 with a diameter between 5microns and 5 centimeters. There may be hundreds of thousands ormillions of meta-atoms patterned on the meta-surface 120 of themeta-lens 100, and a diameter of the area over which the meta-atoms arepatterned may be between 100 um and 50 mm. A thickness of the meta-lensmay be between 50 microns for membranes and 50 mm, and a focal length ofthe meta-surface can be between 0.1 mm and 50 mm.

FIG. 4 depicts an example of an ocular imaging system 400 that uses acompact meta-lens 410. The ocular imaging system 400 can include themeta-lens 410 spaced apart from an integrated circuit 480 and anaperture stop (which is the pupil of the eye in the illustratedexample). The meta-surface of the meta-lens 410 and integrated circuit480 may be separated by a distance having a value between 0.1 mm and 50mm and may be mounted together within a common case. The case mayinclude adjustment mechanisms, such as screws and/or piezoelectricpositioners, to adjust one or more of parallelism, distance, lateralposition, and rotation between the meta-lens 410 and the integratedcircuit 480. The meta-lens can be designed as a wide FOV lens, e.g., aFOV between 70° and 200° as described above, to form an image of a largeportion of the retina onto the flat integrated circuit 480. The ocularimaging system 400 may be specified for use (or designed for use) withina certain distance from the eye (for example, a distance of 2 mm and 100mm between the meta-surface of the lens and the pupil of the subject'seye being examined), so that the eye's pupil functions as an aperturestop for the imaging system. When located closer to the eye, thediameter of the meta-lens can be reduced compared to a meta-lens locatedfarther from the eye. For example, when located close to the eye, thearea on the meta-surface 120 that includes meta-atoms for wide FOVimaging may have a diameter between 5 mm and 15 mm.

In some implementations, the case supporting the meta-lens 410 andintegrated circuit 480 may be formed to contact the subject's foreheadand/or cheek bone to hold the meta-lens at a suitable distance from thesubject's eye and pupil. Because the ocular imaging system 400 mayinclude only a meta-lens 410 and integrated circuit 480, the casesupporting these elements may be no more than 20 mm thick and maymeasure no more than 60 mm on a side in some cases, or no more than 100mm on a side in some implementations. A volume of the ocular imagingsystem 400 may be no greater than 60 cm³ in some cases, or no more than100 cm³ in some implementations.

The integrated circuit 480 can include an imaging region 486 and one ormore illumination regions 482, which may be formed on a same substrateand/or located on a same plane. The imaging region 486 may contain anarray of photodetectors (e.g., a CCD or CMOS imaging array) along withread-out circuitry. For low light levels, the photodetectors maycomprise avalanche photodiodes. The photodetectors and read-outcircuitry are used to acquire electronic images of the retina or othertissues formed by the meta-lens 410. The integrated circuit 480 mayconnect to a computer or smart phone, so that the electronic images maybe stored and/or processed. An illumination region 482 can include oneor more light-emitting devices (e.g., light-emitting diode(s),vertical-cavity surface-emitting laser(s), laser diode(s), etc.) thatproduce an illumination beam 460. In some implementations, theillumination region 482 can be annular and surround the imaging region486. The illumination beam(s) 460 may be directed at the eye and may ormay not enter the eye through its pupil. For example, the illuminationbeam(s) may enter the eye through the ciliary muscle or sclera andscatter from such tissue to illuminate a large portion of the interioreye and tissues of interest therein. By introducing light into the eyeoff-axis and away from the pupil, back reflections from interfacesthrough the pupil that contribute to imaging noise and/or backgroundsignal can be reduced.

The meta-lens 410 may include an imaging zone 416 that corresponds tothe imaging region 486 and one or more illumination zones 412 thatcorrespond to the illumination region(s) 482 of the integrated circuit480. The imaging zone 416 and illumination zone(s) 412 can include aplurality of meta-atoms formed on the meta-surface of the meta-lens 410.In some cases, the meta-atoms are formed on a back surface of themeta-lens that is away from the eye. In other cases, the meta-atoms maybe formed on a front surface of the meta-lens that is closest to theeye. In yet other cases, meta-atoms may be formed on the front and backsurfaces of the meta-lens 410.

Meta-atoms formed in the imaging zone 416 can be as described above toimage a wide FOV of the retina onto the flat imaging region 486 of theintegrated circuit 480. In addition to correcting for Seidelaberrations, these meta-atoms may also account for changes in objectdistances to different portions of the retina. Meta-atoms formed in theillumination zone(s) 412 can be arranged to collimate or focus lightfrom emitters in the illumination region 482 onto the eye. Accordingly,the pattern and functionality of meta-atoms in the illumination zone(s)412 can differ from the pattern and functionality of meta-atoms in theimaging zone 416.

In operation, light emitted from emitters in the illumination region(s)482 is coupled by the illumination zone(s) 412 to illuminate the retinaor other tissues of interest in the eye. Light reflected by the retinaor other tissues is coupled by the imaging zone 416 onto the imagingregion 486 to generate images of the retina or other tissues over a wideFOV. In one example, the illumination beams 460 from the illuminationregion(s) 482 are coupled by at least one illumination zone 412 of themeta-lens 410 to illuminate the pupil, palpebral, scleral, and/orpars-planar with a prescribed pattern (e.g., a ring pattern) to eitherdirectly or diffusely illuminate the retina. This illumination may yielda large, uniformly-illuminated retinal region and exhibit reduced backreflections from the cornea into the imaging optical path. The eye'spupil acts as an aperture stop for the meta-lens and optical system toachieve high-resolution images over the wide FOV.

Although the emitters, photodetectors, illumination zone(s) 412 andimaging zone 416 are segregated on their respective substrates in theillustrated example of FIG. 4, they may not be segregated in otherimplementations. For example, the illumination zone(s) 412 and imagingzone 416 can be overlapped to achieve multiplexed functions in a samearea of the meta-lens 410. This is possible because of the flexibledesign offered by shaping and arranging the meta-atoms on the lens'meta-surface. In an overlapped configuration, the emitters may belocated (e.g., interspersed) within a same area of the integratedcircuit 480 as photodetectors.

Additionally, optical filtering is possible with the meta-atoms on thelens' meta-surface. An optical filter may be used to allow a desiredrange of wavelengths to be passed or rejected. The meta-atoms can bedesigned to provide such additional functionalities. For example,silicon nano-posts can be designed to block light with wavelengthsshorter than approximately 650 nm while passing longer wavelengths forimaging.

The ocular imaging system 400 of FIG. 4 can exhibit several improvementsover conventional ocular imaging systems. The ocular imaging system 400can exhibit an improved single-shot FOV having a value between 70° and200°. Larger FOVs may be possible with curved substrates or otheroptical arrangements as described further below. These FOV values areexpressed in terms of eye angle (i.e., measured as a spherical anglearound the interior of the eye) rather than external incidence angle.Such large FOVs are a significant improvement over conventional funduscameras that typically achieve a single-shot FOV up to about 60°.Conventional fundus cameras are limited by the acceptance angle of bulkyoptical lens systems that correct angle-induced aberrations and anunavoidable distance between the eye's pupil and entrance aperture ofthe bulky lens system. Although some conventional fundus cameras withmoving components (scanning mirrors) can achieve very high FOVs, thesecameras are mechanically complicated, expensive, and require a skilledoperator in a clinical setting.

The ocular imaging system 400 can exhibit improved illumination andimaging co-assemblies. For example and as seen in FIG. 4, a samesubstrate for the meta-lens 410 can be used for forming images of theinterior eye and for shaping and guiding illumination light into theeye. Additionally, the photodetectors for imaging and emitters forillumination may be mounted on a same plane and/or substrate or onparallel planes. In contrast, illumination and imaging paths ofconventional fundus cameras usually involve complex and bulky opticalsystem that form a common optical path for illuminating and imaging theretina. Some traditional fundus cameras illuminate directly through thepupil (i.e., trans-pupillary illumination) by generating a ring-shapedpattern around the peripheral region of the pupil to minimize backreflection. Such designs are typically complex with limited FOV and poorillumination uniformity. Additionally, pupillary dilation is oftenrequired. Trans-scleral, trans-palpebral, and trans-pars-planarillumination methods have been proposed for wide-FOV fundus imagingwithout the need for pupil dilation. However, in such conventionalapproaches external light sources (e.g., LEDs or fiber-coupled sources)are brought in close proximity to the eye to illuminate the retina. Suchseparately-assembled illumination units, sometimes in direct contactwith the eye lid, demand precise alignment and pose challenges fordevice miniaturization.

The ocular imaging system 400 can further exhibit improvedsignal-to-noise ratios over conventional systems. Off-axis illuminationof the retina by introducing light through regions of the eye other thanthe pupil (as depicted in FIG. 4) can reduce glare (noise) that wouldotherwise arise from reflections from multiple optical surfaces if theillumination light were introduced along an imaging path through thepupil (as done for most conventional fundus cameras). Such a reductionin glare is beneficial for improving signal-to-noise since the desiredsignal is a weak reflection of illumination light from the retina orother tissues of interest.

Another advantage of the ocular imaging system 400 is that the system'smeta-lens can be readily designed for operation at a single wavelength,multiple wavelengths, or a broad range of wavelengths. One or morelight-emitting devices can be included in the integrated circuit 480 toemit light at the desired operating wavelength(s). Once the operatingwavelength(s) is or are known, numerical computation is performed todesign the shape and arrangement of meta-atoms on the lens' meta-surfaceto achieve desired imaging and illumination functionality. Operatingwavelengths may include visible to IR wavelengths. For example, visiblewavelengths can be used for near-eye display. One or more of visible,near IR, and longer wavelength IR may be used for ocular imaging.

Because of their small size and low part count, in some cases themeta-lens 410 and/or integrated circuit 480 may be swappable during use.As one example, there may be a plurality of meta-lenses 410 and/orintegrated circuits 480 on a wheel that are designed to operate atdifferent wavelengths. A first selected pair or an integrated circuit480 may be rotated into position to obtain first ocular images at afirst wavelength or range of wavelengths. The first wavelength(s) may bedesigned to preferentially image blood vessels, for example. A secondpair or an integrated circuit 480 may then be rotated into position toobtain second ocular images at a second wavelength or range ofwavelengths. The second wavelength(s) may be designed to preferentiallyimage retinal tissue, for example. In some cases, rotatable componentsmay not be necessary. Instead, a single meta-lens 410 may be designed toprovide sufficient imaging for all wavelengths of interest and differentemitters may be included on the same integrated circuit 480. In such acase, the different emitters may be cycled on and off in sequence toilluminate the eye with a sequence of different wavelengths.

Other meta-lens structures and ocular imaging systems are also possible.FIG. 5A, FIG. 5B, and FIG. 5C depict ray-tracing results for severalocular imaging systems 500, 502, 504 having different meta-lens designs.For each of the designs, the meta-lens comprises a sapphire substrate.The meta-atoms are formed from silicon and all are shaped as cylindricalnano-pillars 540 of various diameters, of which an example is depictedin the inset of FIG. 5A. There is a sub-wavelength spacing between thepillars. In these designs, the pupil of the eye is used as the aperturestop of the ocular imaging system to achieve high-resolution images overa wide FOV. The ray-tracing model assumes a pupil diameter of 4 mm and a4 mm separation distance between the cornea and the front surface of themeta-lens. In some cases with different meta-lens design, the separationdistance may be between 2 mm and 100 mm. Meta-atoms 540 are patterned ona back surface of the meta-lens and image the retina onto a focalsurface 550, 552 over a wide FOV with significantly reduced aberrations.The meta-lens is designed to have an effective f-number of between 0.5and 10, though other values can be readily achieved with differentdesign of the meta-lens. The total thickness of the ocular imagingsystem (excluding the pupil) can be between 5 mm and 50 mm with a singlefocusing optical element.

In FIG. 5A, the meta-lens 510 has a planar back surface on which siliconnano-pillars 540 are patterned. These meta-atoms focus incoming raysonto a flat focal plane 550, where an integrated circuit may be located.The front surface of the meta-lens 510 can be curved (e.g., sphericallyconcave) as shown. With a different arrangement of meta-atoms, the frontsurface of the meta-lens 510 may be flat as depicted in FIG. 4. The FOVfor the illustrated meta-lens is over 180°, as measured around theinterior of the eye.

FIG. 5B illustrates another implementation where the meta-lens 512comprises a curved substrate. The meta-atoms may be formed on the backsurface of the substrate when the substrate is flat, and the substratemay be subsequently deformed (e.g., suctioned under vacuum or heated anddeformed into a spherically-shaped shell). The meta-atoms are arrangedto focus the rays onto a flat focal plane 550. The FOV for theillustrated meta-lens is over 180°.

FIG. 5C illustrates another implementation where the meta-lens 514comprises a curved substrate. The meta-atoms may be formed on the backsurface of the substrate and are arranged to focus the rays onto acurved focal surface 552. The eye-angle FOV for the illustratedmeta-lens is over 180°. For such an implementation, the integratedcircuit may be formed on a flat and flexible substrate that issubsequently deformed into a spherical shape.

By including at least one curved surface on a meta-lens and/or focusingto a curved focal plane as depicted in FIG. 5A through FIG. 5C, the FOVmay be increased significantly (e.g., by at least 30°) over the FOV forthe implementation shown in FIG. 4. Potentially, the entire retina maybe imaged in a single shot with such ocular imaging systems, which isnot possible with conventional ocular imaging systems. Introducingcurved surfaces may facilitate other 3D imaging, sensing, orillumination functions. The ability to flexibly design wavefront shapingwith the meta-lens allows geometric modifications of the meta-lenssubstrate and/or focal plane, which can be decoupled from the system'soptical functionality. Such geometric modifications may significantlyimprove light capturing at large angles, facilitate system integration,and allow ergonomic designs tailored for human body shapes forapplications such as ocular imagers, wearable medical devices, headmounted displays, etc. In some cases, a conformal opticalmeta-lens-based system can be placed in contact with the eye, forexample, by integration into a contact lens. In addition, both substratesurfaces of a meta-lens can be patterned with meta-atoms to furtherenhance wavefront control.

FIG. 6 depicts another implementation of an ocular imaging system 600 ornear-eye display system in which a relay optic 620 is used between theeye and meta-lens 610. When a relay optic 620 is used, the meta-lens 610may include an aperture stop and aperture on a front surface of thesubstrate, as depicted in FIG. 1. The relay optic can relay an image ofthe eye's pupil onto the meta-lens' input aperture, so that theseparation between the pupil and meta-lens does not limit the FOV of theocular imaging system. The relay optic 620 may be a large spherical,ellipsoidal, or parabolic reflector or a large lens. Relaying the pupilonto the meta-lens' input aperture allows the angle-of-incidence on themeta-lens' aperture to be increased up to nearly ±90°, thus utilizingthe full FOV of the meta-lens 610. One implementation of the relay optic620 can be an ellipsoidal reflector in which the eye pupil and themeta-lens input aperture are positioned at the reflector's two foci, sothat light emitted from one point near the first focal point convergesto a point near the second focal point. Another implementation of therelay optic 620 is a freeform reflector. Yet another implementation ofthe relay optic 620 is a meta-surface, diffractive optical elements,holographic optical elements designed to, for example, produce constantoptical path lengths between the eye pupil and the meta-lens' inputaperture. Yet another implementation of the relay optic 620 is ameta-surface formed on a curved surface, e.g., a reflectivemeta-surface. An integrated circuit 480 having photodetectors andlight-emitting devices can be located at a focal plane 150 of themeta-lens 610 for illumination and image acquisition.

Using a relay optic 620 can allow the meta-lens 610 to be locatedfarther from the eye than in previous embodiments, e.g., up to 200 mm.However, larger effective optical path distances between the eye andmeta-lens 610 may require larger-diameter relay optics. For example, ata distance of 200 mm, the diameter of the relay optic may be between 100mm and 200 mm.

The ocular imaging systems described above may be used in reverse toperform near-eye projection of an image onto the retina. For example,the image sensor (photodetectors) may be replaced or augmented by alight emitter array or micro-display 780, as depicted in the near-eyedisplay system 700 of FIG. 7. The emitter array or micro-display 780 canbe used to form images that are projected by the meta-lens 710 over awide FOV (e.g., between 70° and 200°) onto the retina for user viewing.The emitter array or micro-display 780 may be located within 10 mm fromthe meta-lens 710, which can be located within 40 mm or within 100 mm ofthe pupil. FIG. 7 depicts emission from three point sources of an imageto simplify the drawing, but in practice emission can be from anextended and continuous image over part or all of the emitter-array ormicro-display 780. In some cases, a curved and/or conformal opticalsystem (such as that depicted in FIG. 5C) can be configured for near-eyedisplay and placed in contact with the eye (e.g., by integration into acontact lens). One or more near-eye display systems 700 may be providedfor each eye for stereo and/or 3D display.

Additionally or alternatively to direct projection of the image onto theretina, a relay and/or combiner optic can be included to redirect thelight emitted from the meta-lens towards the eye, similar to the ocularimaging systems described in connection with FIG. 6. The combiner cancombine the projected image with other optical beams. For example, in asee-through configuration in AR systems, the projected image can becombined with the scene of the outside world that would normally beviewed by the user. The relay and/or combiner optics can be in the formof meta-optics, diffractive optical elements, holographic opticalelements, beam splitters, refractive or reflective optics, waveguideoptics, etc.

In a near-eye display system, the wide FOV meta-lens can readily enableadvanced light manipulation emitted towards the eye with high-qualitybeam shaping, collimation, focusing, steering, and image/patternprojection with high angular resolution. Such functionality, along withaberration-free imaging, is desirable for a variety of applicationsbeyond retinal illumination/imaging, such as AR/VR. The above-describedmeta-lens based imaging and near-eye display systems (and eye-trackingsystems described below) are fully compatible with integration ofstate-of-the-art micro-LED emitter arrays, micro-displays, and imagesensor arrays (now available with less than 3 micron pitch). Suchnear-eye display systems can have the same form factor, power, and costadvantages of the ocular imaging systems described above. Accordingly,AR and VR systems using meta-lenses can be small, lightweight, andexhibit very large FOVs for user convenience and improved realism.

Meta-lens based optical systems may also be used for eye-trackingapplications. Eye-tracking technology can be useful for suchapplications as human-computer interaction, cognitive science, marketingresearch, AR/VR, human factors, ergonomics, psycholinguistics,neurological diagnosis, and so on. Eye-tracking technology can be usefulfor head-mounted displays which may rely on eye movement to realize userinteractions.

Eye-tracking systems measure the eyes' gazing point, orientation, and/orposition. Video-based, optical eye-tracking systems typically include alight source or a pattern projector that illuminates the eyes with oneor more beams (usually in the near-IR) and an imager that images theeyes and the reflected beam or pattern of beams. Information about theeyes' gazing point, orientation, and/or position can be extracted byanalyzing the captured image and/or reflected optical signals. Forexample, the corneal reflection and the center of the pupil can be usedas features to determine the gazing point, orientation, and/or positionof an eye. Reflections from different eye tissues can also be used asfeatures for tracking, such as the front of the cornea and the back ofthe lens. Features inside the eye (e.g., retinal blood vessels) can alsobe used for more precise eye tracking, which may demand a more compleximaging configuration. The eye-tracking implementations described beloware well-suited for wearable or head-mounted devices and can be combinedwith near-eye display systems described above. The combination of thenear-eye display and eye-tracking functions using a meta-lens basedplatform can enable ultra-compact AR/VR systems with a robust, lowcomplexity, thin, and light-weight apparatus having no moving parts.

FIG. 8A depicts an eye-tracking system 800 that includes two meta-lenses810, 812. The eye-tracking system 800 also includes an emitter 820 andan imager 830. The meta-lenses 810, 812, emitter 820, and imager 830 canbe mounted on a frame or substrate 802, which may be the frame ofeyeglasses, a transparent lens, screen, or visor, for example,positioned in front of a user's eye. The meta-lenses 810, 812 may beoriented to a same plane or parallel planes. The emitter 820 may includeone or more light-emitting devices that emit light (e.g., near-infraredlight) toward a first meta-lens 810. The first meta-lens may form one ormore beams that are projected onto the eye. The one or more beams mayilluminate one or more of the cornea, fundus, retinal blood vessels,pupil, etc.

A second meta-lens 812 may be arranged on an opposite front side of theeye and designed to image light reflected from the eye onto an imager830. The arrangement of meta-atoms on the second meta-lens may differfrom the arrangement of meta-atoms on the first meta-lens 810. Theimager can include an array of photodetectors to record electronicimages of the eye. The imager 830 may be in communication with aprocessor (e.g., a microcontroller, digital signal processor,microprocessor, or some combination thereof) so that recorded images ofthe eye can be processed to track eye movement and determine gazingpoint, orientation, and/or position of the eye.

FIG. 8B depicts an example of an eye-tracking system 802 in which thefunctionalities of illumination and imaging are combined onto samesubstrates (similar to that described above for the ocular imager ofFIG. 4). For example, two meta-lenses 840 may have identicalarrangements of meta-atoms on their meta-surfaces. Each meta-lens mayinclude an illumination zone 842 and an imaging zone 846. Similarly,each integrated circuit 850 may include an emitter region withlight-emitting devices and an imaging region with photodetectors. Eachintegrated circuit 850 and meta-lens 840 may, in part, project one ormore beams onto the eye, and each integrated circuit 850 and meta-lens840 may, in part, image light reflected from the eye to track eyemovement. As with the imager of FIG. 4, in other implementations thefunctionalities of illuminating and imaging may be spatially overlappedon the meta-lenses 840 and integrated circuits 850.

The eye-tracking optical systems of FIG. 8A and FIG. 8B may be arrangedon a curved surface, as depicted in the example of FIG. 8C. For example,the first meta-lens 810, second meta-lens 812, emitter 820, and imager830 may be mounted in two separated modules that can be orientedtangentially to a spherical surface 870. A curved surface configurationcan improve light capturing at large angles, may facilitate systemintegration, and allow ergonomic designs tailored for human body shapesfor applications such as wearable and head mounted devices. In somecases, at least part of the curved and/or conformal eye-tracking systemmay be placed in contact with the eye, for example, by integration intoa contact lens. For example, an emitter 820 and its meta-lens may beintegrated into a contact lens, and an imager 830 and its meta-lens maybe mounted external to the eye. Alternatively, the imager and its lensmay be integrated into a contact lens and the emitter and its lensexternal to the eye.

For the above-describe eye-tracking systems and display systems, themeta-surface of a meta-lens can be encoded with meta-atoms to allocatedifferent zones for different light-manipulation tasks. Alternatively, ameta-surface can be encoded to multiplex different functional zones andlight-manipulation tasks together over a shared region of the meta-lens.Light emitters can be coupled with the illumination zone(s) of ameta-lens to generate two-dimensional or three-dimensional spot arraysand/or illumination patterns on the tissues of interest. In some cases,a single light emitter can be coupled with an illumination zone (e.g., ameta-surface designed as a holograph or spot generator) to generate2D/3D spot arrays and/or illumination patterns. Light reflected bytissue is coupled by the imaging zone onto the photodetectors togenerate electronic images. The meta-lenses of the eye-tracking systemsmay be located within 40 mm or within 100 mm of the eye's pupil andwithin 10 mm of the emitter or imager.

For some implementations, the entire meta-surface can be designed togenerate and image multiple spot arrays and/or illumination patterns ondifferent tissues or different locations in three-dimensional space andto track them separately. The imaging meta-lens can be designed tocapture images at different depths or from different tissues. Themeta-surface can also be designed to illuminate and image an object fromdifferent angles to generate a 3D image for stereo imaging, for example.Additionally, a meta-surface can be designed to providewavelength-filtering functionality. For example, amorphous-Si nano-postscan be designed to block light with wavelengths shorter thanapproximately 650 nm while passing longer wavelengths.

The small form factor of the meta-lens based imagers, near-eye displays,and eye-trackers can allow multiple projection and imagingsub-modules/sub-zones to be integrated at different locations in anocular device, as is done for the example systems of FIG. 8A, FIG. 8B,and FIG. 8C. Multiple modules may be useful for stereo and/or 3D imagingand projection. Two or more modules may be used for each eye. Eachmodule may include multiple zones for pattern projection and imagingfunctionalities, as described above.

The above-described wide FOV meta-lenses can be relativelystraightforward to fabricate using conventional micro-fabricationtechnologies. Fabrication methods can include patterning resist andperforming lift-off or etching process steps. Example fabricationmethods are described in U.S. patent application Ser. No. 16/894,945titled “Ultra-Wide Field-of-View Flat Optics,” filed Jun. 8, 2020, whichdescription of fabrication is incorporated herein by reference. Themeta-lenses can be designed to operate at a wide range of wavelengths(e.g., from ultraviolet to microwave frequencies with a bandwidth thatspans up to an octave), depending on the selected design and arrangementof meta-atoms and the substrate and meta-atom materials.

Methods of operating a meta-lens based ocular imaging, near-eye display,or eye-tracking system are possible with the above-describedembodiments. FIG. 9 depicts acts that may be performed when operating anocular imaging system, for example. Such a method 900 may include actsof directing (act 910) light from a light-emitting device toward an eyeand operating (act 920) on the light with one or more illumination zonesof one or more meta-lenses. Operating on the light may comprisingcollimating, focusing, or patterning the light (e.g., forming a patternof spots or forming an image) with the one or more illumination zones.The method 900 may further include operating (act 930) on lightreflected from eye tissue with one or more imaging zones of one or moremeta-lenses. Operating on the reflected light may comprise focusing thelight onto sensors (e.g., photodetectors) of one or more integratedcircuits located behind the meta-lens(es). The sensors may then be usedto record (act 940) an image. The method 900 may further includeprocessing recorded images to detect a physical condition of the eye orto detect movement of the eye (e.g., performing eye-tracking).

Various configurations of meta-lens-based ocular imaging apparatus andmethods of operating the imaging apparatus are included as set forthbelow.

(1) An ocular imaging system comprising: a substrate having a firstmeta-surface formed thereon, the meta-surface comprising an imaging zonehaving a first plurality of meta-atoms, wherein the meta-surface is tobe positioned within 100 mm of an eye's pupil to image an interiorportion of the eye; a light source to illuminate an interior of the eye;and an array of photodetectors located at a focal surface of themeta-surface to detect an image of the interior portion of the eye thatis formed by the imaging zone.

(2) The ocular imaging system of configuration (1), wherein the pupil ofthe eye acts as an aperture stop for the ocular imaging system to obtainhigh-resolution images.

(3) The ocular imaging system of configuration (1) or (2), furthercomprising an illumination zone on the substrate formed from a secondplurality of meta-atoms, the second plurality of meta-atoms arranged tocollimate, focus, or pattern light from the light source onto the eye.

(4) The ocular imaging system of any one of configurations (1) through(3), wherein the light source comprises one or more light-emittingdiodes adjacent to the array of photodetectors.

(5) The ocular imaging system of configuration (4), wherein a totalthickness of the ocular imaging system is no greater than 20 mm.

(6) The ocular imaging system of configuration (4) or (5), wherein atotal volume of the ocular imaging system is no greater than 100 cm3.

(7) The ocular imaging system of any one of configurations (1) through(6), wherein the substrate comprises sapphire, silica, calcium fluoride,or a polymer.

(8) The ocular imaging system of configuration (7), wherein the firstplurality of meta-atoms are formed from a dielectric, semiconductor, ormetal material.

(9) The ocular imaging system of any one of configurations (1) through(8), wherein the first plurality of meta-atoms comprises meta-atoms ofat least two different shapes or sizes that are repeated across thesubstrate.

(10) The ocular imaging system of any one of configurations (1) through(9), wherein the substrate has at least one curved surface.

(11) The ocular imaging system of configuration (10), wherein the focalsurface is curved.

(12) The ocular imaging system of any one of configurations (1) through(11), further comprising: an aperture stop formed on a second surface ofthe substrate; and a relay optic to relay an image of the pupil of theeye onto an aperture formed by the aperture stop.

The following methods may be used to operate ocular imaging systems ofone or more of the above configurations and following configurations.

(13) A method of operating an ocular imaging system, the methodcomprising: directing light from a light source toward an eye;collimating, focusing, or patterning the light with an illumination zoneof a meta-surface, the illumination zone comprising a first plurality ofmeta-atoms formed on a substrate; focusing light reflected from the eyewith an imaging zone of the meta-surface, the imaging zone comprising asecond plurality of meta-atoms formed on the substrate; and detectingthe focused light with an array of photodetectors.

(14) The method of (13), further comprising using the pupil of the eyeas an aperture stop for the ocular imaging system.

(15) The method of (13) or (14), further comprising forming an image ofa retina of the eye having a field-of-view that is between 70 degreesand 200 degrees as measured around the interior of the eye.

The following configurations may include one or more features from anyone of configurations (1) through (12) above.

(16) A near-eye display system comprising: a substrate having ameta-surface formed thereon, the meta-surface comprising a plurality ofmeta-atoms, wherein the meta-surface is to be positioned within 100 mmof an eye's pupil; and a micro-emitter array or micro-display locatedwithin 10 mm of the meta-surface to form an image that is projected bythe meta-surface onto the retina of the eye, wherein the image covers afield-of-view between 70 degrees and 200 degrees as measured around theinterior of the eye.

(17) The near-eye display system of configuration (16), wherein thenear-eye display system utilizes the pupil as an aperture stop to obtainhigh resolution image projection.

(18) The near-eye display system of configuration (16) or (17), whereinthe substrate is formed of sapphire and the meta-atoms are formed ofsilicon.

(19) An eye-tracking system comprising: an emitter to produceillumination light; a first meta-surface that is within 10 mm of theemitter and within 40 mm or within 100 mm of an eye's pupil, the firstmeta-surface including a first plurality of meta-atoms formed on asurface of a first substrate and arranged to project a pattern of theillumination light onto the eye; a second meta-surface located within 40mm or within 100 mm of the eye's pupil, the second meta-surfaceincluding a second plurality of meta-atoms arranged to image a region ofthe eye illuminated by the pattern; and an imager having a plurality ofphotodetectors to record an image of the region of the eye.

(20) The eye-tracking system of configuration (19), wherein the secondmeta-surface is formed on a surface of a second substrate that isseparated from the first substrate, and wherein the first meta-surfaceand the second meta-surface lie in a same planar surface or lie inparallel planar surfaces.

(21) The eye-tracking system of configuration (19), wherein the secondmeta-surface is formed on a surface of a second substrate that isseparated from the first substrate, and wherein the first meta-surfaceand the second meta-surface lie on a curved surface.

(22) The eye-tracking system of any one of configurations (19) through(21), wherein the second meta-surface is formed on the surface of thefirst substrate, and wherein the emitter and the imager are located on asame substrate.

While various inventive implementations have been described andillustrated herein, those of ordinary skill in the art will readilyenvision a variety of other means and/or structures for performing thefunction and/or obtaining the results and/or one or more of theadvantages described herein, and each of such variations and/ormodifications is deemed to be within the scope of the inventiveimplementations described herein. More generally, those skilled in theart will readily appreciate that all parameters, dimensions, materials,and configurations described herein are meant to be exemplary and thatthe actual parameters, dimensions, materials, and/or configurations willdepend upon the specific application or applications for which theinventive teachings is/are used. Those skilled in the art will recognizeor be able to ascertain, using no more than routine experimentation,many equivalents to the specific inventive implementations describedherein. It is, therefore, to be understood that the foregoingimplementations are presented by way of example only and that, withinthe scope of the appended claims and equivalents thereto, inventiveimplementations may be practiced otherwise than as specificallydescribed and claimed. Inventive implementations of the presentdisclosure are directed to each individual feature, system, article,material, kit, and/or method described herein. In addition, anycombination of two or more such features, systems, articles, materials,kits, and/or methods, if such features, systems, articles, materials,kits, and/or methods are not mutually inconsistent, is included withinthe inventive scope of the present disclosure.

Also, various inventive concepts may be embodied as one or more methods,of which an example has been described. The acts performed as part ofthe method may be ordered in any suitable way. Accordingly,implementations may be constructed in which acts are performed in anorder different than illustrated, which may include performing some actssimultaneously, even though shown as sequential acts in illustrativeimplementations.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.”

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” can refer,in one implementation, to A only (optionally including elements otherthan B); in another implementation, to B only (optionally includingelements other than A); in yet another implementation, to both A and B(optionally including other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one implementation, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another implementation, to at least one, optionallyincluding more than one, B, with no A present (and optionally includingelements other than A); in yet another implementation, to at least one,optionally including more than one, A, and at least one, optionallyincluding more than one, B (and optionally including other elements);etc.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively, as set forth in the United States Patent Office Manual ofPatent Examining Procedures, Section 2111.03.

1. An ocular imaging system comprising: a substrate having a firstmeta-surface formed thereon, the meta-surface comprising an imaging zonehaving a first plurality of meta-atoms, wherein the meta-surface is tobe positioned within 100 mm of an eye's pupil to image an interiorportion of the eye; a light source to illuminate an interior of the eye;and an array of photodetectors located at a focal surface of themeta-surface to detect an image of the interior portion of the eye thatis formed by the imaging zone.
 2. The ocular imaging system of claim 1,wherein the pupil of the eye acts as an aperture stop for the ocularimaging system to obtain high-resolution images.
 3. The ocular imagingsystem of claim 1, further comprising an illumination zone on thesubstrate formed from a second plurality of meta-atoms, the secondplurality of meta-atoms arranged to collimate, focus, or pattern lightfrom the light source onto the eye.
 4. The ocular imaging system ofclaim 1, wherein the light source comprises one or more light-emittingdiodes adjacent to the array of photodetectors.
 5. The ocular imagingsystem of claim 4, wherein a total thickness of the ocular imagingsystem is no greater than 20 mm.
 6. The ocular imaging system of claim4, wherein a total volume of the ocular imaging system is no greaterthan 100 cm³.
 7. The ocular imaging system of claim 1, wherein thesubstrate comprises sapphire, silica, calcium fluoride, or a polymer. 8.The ocular imaging system of claim 7, wherein the first plurality ofmeta-atoms are formed from a dielectric, semiconductor, or metalmaterial.
 9. The ocular imaging system of claim 1, wherein the firstplurality of meta-atoms comprises meta-atoms of at least two differentshapes or sizes that are repeated across the substrate.
 10. The ocularimaging system of claim 1, wherein the substrate has at least one curvedsurface.
 11. The ocular imaging system of claim 10, wherein the focalsurface is curved.
 12. The ocular imaging system of claim 1, furthercomprising: an aperture stop formed on a second surface of thesubstrate; and a relay optic to relay an image of the pupil of the eyeonto an aperture formed by the aperture stop.
 13. A method of operatingan ocular imaging system, the method comprising: directing light from alight source toward an eye; collimating, focusing, or patterning thelight with an illumination zone of a meta-surface, the illumination zonecomprising a first plurality of meta-atoms formed on a substrate;focusing light reflected from the eye with an imaging zone of themeta-surface, the imaging zone comprising a second plurality ofmeta-atoms formed on the substrate; and detecting the focused light withan array of photodetectors.
 14. The method of claim 13, furthercomprising using the pupil of the eye as an aperture stop for the ocularimaging system.
 15. The method of claim 13, further comprising formingan image of a retina of the eye having a field-of-view that is between70 degrees and 200 degrees as measured around the interior of the eye.16. A near-eye display system comprising: a substrate having ameta-surface formed thereon, the meta-surface comprising a plurality ofmeta-atoms, wherein the meta-surface is to be positioned within 100 mmof an eye's pupil; and a micro-emitter array or micro-display locatedwithin 10 mm of the meta-surface to form an image that is projected bythe meta-surface onto the retina of the eye, wherein the image covers afield-of-view between 70 degrees and 200 degrees as measured around theinterior of the eye.
 17. The near-eye display system of claim 16,wherein the near-eye display system utilizes the pupil as an aperturestop to obtain high resolution image projection.
 18. The near-eyedisplay system of claim 16, wherein the substrate is formed of sapphireand the meta-atoms are formed of silicon.
 19. An eye-tracking systemcomprising: an emitter to produce illumination light; a firstmeta-surface that is within 10 mm of the emitter and within 100 mm of aneye, the first meta-surface including a first plurality of meta-atomsformed on a surface of a first substrate and arranged to project apattern of the illumination light onto the eye; a second meta-surfacelocated within 100 mm of the eye's pupil, the second meta-surfaceincluding a second plurality of meta-atoms arranged to image a region ofthe eye illuminated by the pattern; and an imager having a plurality ofphotodetectors to record an image of the region of the eye.
 20. Theeye-tracking system of claim 18, wherein the second meta-surface isformed on a surface of a second substrate that is separated from thefirst substrate, and wherein the first meta-surface and the secondmeta-surface lie in a same planar surface or lie in parallel planarsurfaces.
 21. The eye-tracking system of claim 18, wherein the secondmeta-surface is formed on a surface of a second substrate that isseparated from the first substrate, and wherein the first meta-surfaceand the second meta-surface lie on a curved surface.
 22. Theeye-tracking system of claim 18, wherein the second meta-surface isformed on the surface of the first substrate, and wherein the emitterand the imager are located on a same substrate.